Surg Today DOI 10.1007/s00595-014-0981-6
A persistent sciatic artery aneurysm containing a free‑floating thrombus: report of a case Satoshi Unosawa · Yusuke Ishii · Tetsuya Niino
Received: 27 January 2014 / Accepted: 10 June 2014 © Springer Japan 2014
Abstract A persistent sciatic artery is a rare vascular anomaly in which the sciatic artery, which involutes in the embryonic stage, persists as the blood supply to the lower limb. This vascular anomaly is often associated with aneurysm formation. A persistent sciatic artery aneurysm is a rare cause of peripheral arterial embolic disease. We herein describe the case of a 72-year-old female with a free-floating thrombus in a persistent sciatic artery aneurysm. She underwent iliac-popliteal artery bypass and exclusion of the aneurysm to prevent an embolic event. Keywords Persistent sciatic artery aneurysm · Free-floating thrombus · Iliac-popliteal artery bypass
Introduction A persistent sciatic artery is a rare vascular anomaly in which the sciatic artery, which involutes in the embryonic stage, persists as the blood supply to the lower limb. This vascular anomaly is often associated with aneurysm formation, which leads to sciatica, rupture and embolism from the thrombus in the aneurysm. We herein report a case in which we detected a free-floating thrombus in a persistent sciatic artery aneurysm during follow-up, and performed surgery to prevent an embolic event.
S. Unosawa (*) · Y. Ishii · T. Niino Department of Cardiovascular Surgery, National Hospital Organization Disaster Medical Center, 3256, Midori‑chou, Tachikawa‑shi, Tokyo 190‑0014, Japan e-mail: [email protected]
Case report The patient was a 72-year-old female with a history of hypertension. She visited our hospital with a chief complaint of intermittent claudication at when walking more than 100 m that had been present for 1 month. The anklebrachial index (ABI) was 0.69 on the right and 1.02 on the left, showing decreased blood flow in the right lower limb. The administration of cilostazol was started for suspected arteriosclerosis obliterans. Although the claudication symptoms subsequently disappeared, contrastenhanced computed tomography (CT) was performed because she occasionally noticed pulsation at the hip while in the sitting position. CT revealed bilateral persistent sciatic arteries and an aneurysm with a maximum diameter of 21 mm on the right side. Moreover, a thrombus was observed in the right popliteal artery on CT images (Fig. 1). Because the intermittent claudication had been relieved by drug therapy, the patient was placed under follow-up observation. When a CT study was performed again 18 months later, the persistent sciatic artery aneurysm was found to have grown to 25 mm and to contain a free-floating thrombus, because the thrombus was attached to the arterial wall with circumferential blood flow (Fig. 1). Therefore, the patient was determined to be at high risk of developing an embolic event and was admitted for surgery. On physical examination, the pulse was easily palpated in the peripheral arteries of the lower limbs below both femoral arteries. Moreover, a pulsating mass measuring approximately 3 cm in size was palpated on the outer side of the right ischial tuberosity. The ABI had improved to 1.06 on the right and 1.19 on the left because the thrombus in the right popliteal artery had shrunk (Fig. 1). Surgery was started in the supine
Fig. 1 The preoperative contrast-enhanced computed tomography findings. Bilateral persistent sciatic arteries (white arrow) branching off the internal iliac artery could be seen. The right persistent sciatic artery had enlarged from 21 to 25 mm over a period of 18 months. Part of a thrombus in the aneurysm had become a free-floating thrombus (arrow head). A thrombus (black arrow) was observed in the right popliteal artery on the initial CT, and the thrombus had shrunk 18 months later
position under general anesthesia. The right lower abdomen was incised obliquely. Through the retroperitoneum, the internal iliac artery was detached to the periphery where the inferior gluteal artery branched off, and the internal iliac artery was exposed. The popliteal artery was approached superolaterally from the knee joint and exposed via detachment between the iliotibial band and biceps femoris muscle. We confirmed that the pulsation of the popliteal artery disappeared after blockage of the internal iliac artery. An expanded polytetrafluoroethylene (ePTFE) graft with an 8-mm ring was inserted from the retroperitoneal space, passed under the inguinal ligament and guided to the popliteal fossa through the adductor canal. The vascular graft was anastomosed to the internal iliac artery with an end-to-side anastomosis, and the popliteal artery was transected and then anastomosed to the vascular graft with an end-toend anastomosis. The internal iliac artery was ligated at the periphery of the inferior gluteal artery. The postoperative course was favorable, and the pulsation at the hip also disappeared. Postoperative CT revealed that the graft was fully patent, and that the persistent sciatic
artery aneurysm had been effectively embolized and was shrinking (Fig. 2). The ABI was maintained at 1.00 on the right and 1.19 on the left.
Discussion This patient visited our hospital with a chief complaint of intermittent claudication. Treatment was initially started with arteriosclerosis obliterans in mind. However, CT revealed a localized stenotic lesion in the popliteal artery, and embolism was suggested based on the morphology of the lesion. While there was a persistent sciatic artery aneurysm, no other lesion that could have been an embolic source was detected. Therefore, she was determined to have an embolism from a thrombus within the persistent sciatic artery aneurysm. Although many patients complaining of intermittent claudication have arteriosclerosis obliterans, intermittent claudication symptoms may appear even when the embolism is caused by other diseases, such as an aneurysm, shaggy aorta or left auricular thrombus, if the course is chronic. CT scanning is useful for differentiating these
Fig. 2 The postoperative computed tomography findings. The bypass was patent. The aneurysm had been embolized, showing no contrast enhancement (arrow), and had decreased to 18 mm in maximum diameter
diseases. A persistent sciatic artery can easily be diagnosed by CT, because the artery branches off the internal iliac artery and runs toward the lateral side of the femur. If an aneurysm forms, an embolism from a thrombus in the aneurysm may cause ischemic symptoms affecting the lower limbs. Thus, it is necessary to recognize and consider a persistent sciatic artery in the differential diagnoses of intermittent claudication. A persistent sciatic artery is a vascular anomaly in which the sciatic artery, which involutes and disappears in the embryonic stage, persists. According to a report by van Hooft et al. [1, 2] 70 % of the reported cases was unilateral and 30 % was bilateral. Aneurysm formation was observed in 40–50 % of the reported cases. Persistent sciatic arteries are classified into complete and incomplete types, and the majority of these arteries are of the complete type. In the complete type, the blood in the persistent sciatic artery flows directly into the popliteal artery, and the superficial
femoral artery is hypoplastic. In the incomplete type, there is no direct continuity between the persistent sciatic and popliteal arteries, but the superficial femoral artery is connected to the popliteal artery. The clinical symptoms are due to aneurysmal rupture or lower limb ischemia caused by embolism. Moreover, because the persistent sciatic artery runs along the sciatic nerve, sciatica may be caused by compression due to an aneurysm. The persistent sciatic artery is often detected when patients are examined for ischemic symptoms of the lower limbs, and surgical treatment is often performed to achieve revascularization of the lower limbs. Ikezawa et al.  reported that 31.3 % of symptomatic patients with a persistent sciatic artery had ischemia. Ischemia is generally caused by thrombus in the persistent sciatic artery aneurysm. Anticoagulant treatment might be useful to prevent thrombus formation, because the thrombus is likely formed due to turbulence or stagnation of blood flow in the persistent sciatic artery aneurysm. In our case, because a freefloating thrombus was detected in a persistent sciatic artery aneurysm during follow-up, surgery was performed to prevent an embolism. However, such cases are rare. While surgical treatment for a persistent sciatic artery aneurysm includes exclusion operations, resection and embolization of the aneurysm, the complete type requires revascularization. Because aneurysmectomy is associated with a risk of damaging the sciatic nerve, the aneurysm was excluded without resection in the present case. In our case, the distal branch of the inferior gluteal artery was ligated to reduce the blood supply to the aneurysm as much as possible. In terms of revascularization, the proximal and distal sites of anastomosis are controversial issues. If the femoral artery has developed adequately, it can provide an inflow. However, in cases with hypoplasia, as seen in our present patient, a vascular graft should be anastomosed to the iliac artery. When there is stenosis or an occlusive lesion at a peripheral site, a vascular graft should be anastomosed at the distal site of the lesion. However, as there were no peripheral blood flow problems in this case, despite the stenotic lesion in the popliteal artery below the knee, a vascular graft was anastomosed to the popliteal artery above the knee joint.
Conclusion In our present patient, a persistent sciatic artery aneurysm containing a free-floating thrombus was diagnosed by CT. Iliac-popliteal artery bypass and exclusion of the aneurysm were performed to prevent an embolic event. Conflict of interest The authors have no conflicts of interest.
References 1. van Hooft IM, Zeebregts CJ, van Sterkenburg SM, de Vries WR, Reijnen MM. The persistent sciatic artery. Eur J Vasc Endovasc Surg. 2009;37:585–91. 2. Brantley SK, Rigdon EE, Raju S. Persistent sciatic artery: embryology, pathology, and treatment. J Vasc Surg. 1993;18:242–8.
Surg Today 3. Ikezawa T, Naiki K, Moriura S, Ikeda S, Hirai M. Aneurysm of bilateral persistent sciatic arteries with ischemic complications: case report and review of the world literature. J Vasc Surg. 1994;20:96–103.